A wire-connection condition detection device disclosed in Patent Literature 1 is known as a device that measures electric energy supplied to a load through a power line from a three-phase AC power source. This wire-connection condition detection device determines whether the connection of an alligator clip (terminal) connected with the power line to measure a phase voltage, and the disposition of a clamp sensor (current transformer) disposed on the outer circumference of the power line to measure a phase current are both correct as follow.
This wire-connection condition detection device determines, based on the phase voltage measured through the terminal, whether the effective value of the phase voltage is within a predetermined range, and whether the phase sequence is in the predetermined sequence. In addition, this wire-connection condition detection device also determines, based on the phase voltage measured through the terminal and the phase current measured through the current transformer, whether the phase difference between the phase voltage and the phase current for each phase is within a predetermined range, and whether no phase voltage or phase current is input.
Next, when the effective value of the phase voltage is out of the predetermined range, the phase sequence differs from the predetermined sequence, the phase difference between the phase voltage and the phase current for each phase is out of the predetermined range, or, no phase voltage or phase current is input, this wire-connection condition detection device determines that the terminal is incorrectly connected or the current transformer is incorrectly disposed.